The long-term goal of this research is to elucidate the relationship(s) between mammalian circadian rhythms and the efficiency and health of physiological and behavioral adapatation to environmental challenge or change. In addition to evaluation of behavioral rhythmic parameters, two physiological/biochemical systems or areas are gaining increased emphasis in this work: (1) the use of measurement of dopamine-beta-hydroxylase to monitor output activity of sympathetic and adrenomedullary components; and (2) the study of inputs and mechanisms of the hypothalamic suprachiasmatic nucleus, the central locus of circadian rhythm control. BIBLIOGRAPHIC REFERENCES: 1975. (Quay, W.B.). Intercellular canaliculi in endocrine tissues: distribution, twenty-four-hour rhythmicity and physiological relations. Anatomical Record. 181(2):454. 1976. (Quay, W.B., and Yu-Heng Ma) Photic and circadian factors in changing amino acid uptake by the early postnatal rat's cerebral cortex. Program and Abssracts, 4th Annual Meeting, American Society for Photobiology, pp. 124-125.